Basing cement for lamps and similar devices



Aug. 4, 1942. N. YAMASHITA BASING CEMENT FOR LAMPS AND SIMILAR DEVICES Filed April 22 1941 Inventor- M e a n m r a m Y,.T u A r .s. b H o Patented Aug. 4, 1942 roa LAMPS AND summa- DEVICES aasruc CEMENT FICE Noboru Yamashita, Kawasaki, Kanagawa-ken,

Japan,

assignor to Ge neral ElectricCompany, a

corporation of New York Application April 22, 1941, Serial No.

InJapan April 30, 1940 4 Claims.

My invention relates in general to electric lamps and similar devices of the type comprising I a sealed glass envelope having operative elements and the like sealed thereinto and a base afiixed to a part of the envelope by means of a binding agent or basing cement. More particularly, my invention relates to an improved base construction for such devices.

The glass envelopes and bases of devices of the above-mentioned type are commonly attached to one another by a binder known as a basing cement. Heretofore, such cements were usually formed by mixing an inorganic filler with a binding agent, as for instance, powder of marble, alumina or magnesia and shellac solution. The binding operation is simple, but the the glass envelope and base is not very strong. Consequently, the envelope and base may detach fairly easy when an external force is applied. In order to overcome such defect, it has been customary to impregnate the tively high temperatures. Such a basing cement possesses very high binding power and provides an exceptionally strong bond between the glass envelope and the base.

In the manufacture and subsequent use of the above-mentioned devices, it has been found often necessary or desirable to remove the aflixed base from the envelope, as for instance, when any inferior characteristic of the device is found by test or otherwise, orv when the base is reclaimed as the life of the device terminates. In such cases, the base is removed by applying heat to that portion of the base which is cemented to the glass envelope, the heat carbonizing the basing cement and rendering the binding power thereof ineflective. However, in the case of the aforesaid synthetic resin-impregnated type of basing cement, the cement loses its binding power only after it is heated to an extremely high temperature. Consequently, the base is often inlured or damaged by the intense heat. Even where the base is made of metal there is apt to be such damage from heat, and particularly so where the base is made of a compound, for instance, a synthetic resin such as Bakelite One object of my invention is to provide a cement bond between the base and vitreous envelope of electric lamps and similar devices which will secure the base to the envelope with sumcient rigidity on the one hand while permitting relatively ready removal of the base without damage thereto on the other hand.

A feature of the invention is the use of a cement body which loses its bindingpower at relatively low temperatures and in whichsynthetic resin is impregnated only in a superficial layer in that surface of the cement body which contacts the vitreous envelope.

Further objects and advantages of my invention will be apparent from the following description and from the accompanying drawing in which: i

Fig. 1 is an elevation of a vacuum tube embodying the invention, part of the base being broken away to show the base and basing cement in section, and Fig. 2 is an enlarged cross-sectional view of a portion of the base and envelope and showing the cement bond construction according to the invention.

It is known that separation of lamp bases from the glass envelope is due aration ofthe basing cement from that surface of the glass envelope in contact with the basing cement; and that the binding power of basing cement impregnated throughout with synthetic resin to the glass surface is far greater than that of a basing cement not so impregnated.

According to the invention, for that surface of the basing cement which is to contact the glass envelope a basing cement is used which has been impregnated with synthetic resin, thus utilizing the great bind ngpower of such type basing, cement, while for the surface of the basing cement in contact with the base and in the neighborhood thereof, a cement is used which loses its binding power at relatively low temperatures, i. e., one not so impregnated with synthetic resin.

To form such a composite basing cement conresln on either the inner surface of the layer of basing cement (i. e., that surface which is to contact the glass envelope) or on the surface of the glass envelope which is to be aflixed to the layer of basing cement, then to assemble the base and glass envelope in proper interrelation, and finally to heattreat the assembled parts at the proper temperature to harden or set the basing cement.

Referring to Fig. 1, the invention is there shown in connection with a vacuum tube comprising a sealed envelope I of glass or other primarily to the sepvitreous material having a neck portion 2 and containing one or more electrical energy translation elements (not shown) such as a filament or electrode. A base 3, of an insulating compound or of a metal, surrounds and is secured to 5 cement 4, i. e., the surfaceflrnrnediatelycon tiguous the glass envelope, is impregnated'with" 5* synthetic resin to a proper depth as indicated at 5, i. e;, to a depth sufilcient to-insure that' the surface of the ceme t in contact with" the surface of the glass envelope I is possessedof .the I synthetic resin-impregnated :cementm-L'The' rema iriing portion 5 of the basing cement 4' 0on tiguous to' the base 3, not--being so impregnated.L

with? synthetic" resin, accordingly willwloseiv its; binding power" 'at relatively I low. 1 temperatures. 25

For the sake of cle'a'rness; the impregnatedand; unimpregnated portions 1 5 and B respectivelymf the easingeeme'nt are shownuwith. ardemarca-ytion, mit it will be understood that innthe flctual structure there is no such clear line of demarcatitinf- A r a With such a basing icementr construction; the bond between the glass surface; of ,the envelope and'fthe 'basing cement is sufficiently rigid to-insuieagainstm ture orthe same byasthe :normal; 35

shearing forces "to which it-ais subjected-during the handling and use ofwtheudeyice;. whiie in case the ba'seis to be? removed,:,it; i notynecessai'y to"--heat=;theparts so intensely;as togcar b0nize"the hardened synthetic resin inasmuch as, 4

the bindir'i'g v-power of :the unimpregnated, portion 5 willj 'soon bewlostunder relativelyzlower te peratur'es, therebyrr facilitating the remoy the base' without causing @anya damage th What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electrical device comprising a vitreous envelope having operative elements therein and a base amxed thereto by a layer of bindin cement, the portion of said cement contiguous to ,said basev consisting .offaimaterialwhich loses its binding power at arelatively low temperature and the portion of said cement contiguous "t'o'said vitreous envelope consisting of a material whichlosesits binding power only at a relatively high temperature and which possesses relatively great binding power.

*Anfelectricaldevice comprising a vitreous enyelopej" having "operative elements therein and a base affixed thereto by a layer of basing cement whichloses its binding power at a relatively low :temperature but which has its surface immediately..,contiguous said. vitreous envelope imgreater binding power characteristic of ago' uring togct er al air oi 'mem bers zone; of which is o r vitrjeous material, I said bond comprismg, .alayer of basing cement'. be tween said memberfi wh ch at .a;grelatively, low temperature but which has, its surface immediately contigu u'fs" saidvitre'ous m m errim r na e zw ih e inthereby 'mpart increased g 'poweri to the said contiguous surfacel jpo t f'of. said cement. P 1 1 i'l'ib ii a a a ,t uslme hwhl L comprises a layer q ivbasingcement between said mernbers said cement comprising a I mixt re of inorganic filler and a indingfa'gent iwhich l s i bi in p we -a ti ifl l -t m: perature, the surface .of said nient'imrnediately berbeinei lipres i th syntheticresin to r td'th'e said con:

es itsbin'ding power thereby. impart bindin 

